A pacing catheter and a pulse generator are used to electrically stimulate or pace the heart. To accomplish this, the catheter is inserted through a vein into the heart. Typically, the catheter is inserted into the right ventricle. The catheter may be either unipolar, i.e., have one electrode, or bipolar, i.e., have two electrodes. In either event, the distal electrode of the catheter must be brought into contact with the heart wall in order that pulses of electrical energy can be transmitted from the pulse generator through the catheter to the heart. Pacing of the heart in this fashion is often temporary and may be required, for example, in surgery following a myocardial infarction.
One problem with pacing catheters is that the insertion of the catheter into the heart and into engagement with the heart wall creates a risk of penetration of the heart wall by the catheter. The risk of penetration cannot be avoided by making the catheter uniformly flimsy because the catheter must have enough stiffness to be inserted into the heart. In addition, the catheter must have some resilience so that it can maintain the electrodes in substantially continuous contact with the heart wall in the presence of factors such as the beating of the heart and patient movement, which tend to interrupt engagement between the electrodes and the heart wall.
It is known to provide a flexible tail on a heart stimulation catheter and to space the electrodes proximally from the tail as shown in Harmjanz U.S. Pat. No. 3,664,347. In this construction, the tail must be in an artery of the lungs and neither of the electrodes is at or near the distal end of the catheter.
One way to insert a cardiac pacing catheter or other inner catheter is to advance it through the lumen of a pulmonary artery guiding catheter. To accomplish this, the guiding catheter must first be inserted through a vein and the right heart to the pulmonary artery, and this requires that the guiding catheter be formed into a curve in the right ventricle. The guiding catheter has a port within or adjacent the curve through which the pacing catheter can extend. One problem with this composite guiding catheterpacing catheter system is that the guiding catheter tends to form a sharp reverse bend or kink immediately distally of the port, and this is undesirable in that the kink can close off the lumens in the guiding catheter.
The guiding catheter is of necessity flexible, long and of very small diameter. It is inherently difficult to control the orientation of the port in a device of this type because the port tends to rotate about the long axis of the catheter. Proper control of the angular orientation of the port is important because port orientation materially influences the location of the pacing catheter in the heart.